todos/UnitTests/Tests/Extensions/TodoFetchDescriptorTests.swift

import Foundation
import SwiftData
import Testing

@testable import Todos

@Suite("FetchDescriptor<Todo> extension tests")
struct TodoFetchDescriptorTests {

    // MARK: Initialization tests
    
    @Test(
        "initializes with group when empty tasks",
        arguments: TodoGroup.allCases
    )
    @MainActor
    func initializationWhenEmptyTasks(for group: TodoGroup) throws {
        // GIVEN
        let container = try modelContainer
        let context = container.mainContext
        
        // WHEN
        let descriptor = FetchDescriptor<Todo>(group: .today)
        let results = try context.fetch(descriptor)
        
        // THEN
        #expect(results.isEmpty)
    }
    
    @Test(
        "initializes with group when filled tasks",
        arguments: TodoGroup.allCases
    )
    @MainActor
    func initializationWhenFilledTasks(for group: TodoGroup) throws {
        // GIVEN
        let container = try modelContainer
        let context = container.mainContext
        
        insert(into: context)
        
        // WHEN
        let descriptor = FetchDescriptor<Todo>(group: group)
        let results = try context.fetch(descriptor)
        
        // THEN
        #expect(results.count == 2)
        
        switch group {
        case .completed:
            #expect(results[0].title == "Completed task #2")
            #expect(results[1].title == "Completed task #1")
        case .overdue:
            #expect(results[0].title == "Overdue task #2")
            #expect(results[1].title == "Overdue task #1")
        case .today:
            #expect(results[0].title == "Today task #1")
            #expect(results[1].title == "Today task #2")
        case .upcoming:
            #expect(results[0].title == "Upcoming task #1")
            #expect(results[1].title == "Upcoming task #2")
        }
    }

}

// MARK: - Helpers

private extension TodoFetchDescriptorTests {

    // MARK: Computed

    var modelContainer: ModelContainer {
        get throws {
            try ModelContainer(
                for: Todo.self,
                configurations: .init(isStoredInMemoryOnly: true)
            )
        }
    }

    // MARK: Functions

    func insert(
        into context: ModelContext,
        calendar: Calendar = .current
    ) {
        let tasks: [Todo] = [
            .init(
                title: "Today task #1",
                due: .now
            ),
            .init(
                title: "Today task #2",
                due: .now
            ),
            .init(
                title: "Upcoming task #1",
                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now
            ),
            .init(
                title: "Upcoming task #2",
                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now
            ),
            .init(
                title: "Overdue task #1",
                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now
            ),
            .init(
                title: "Overdue task #2",
                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now
            ),
            .init(
                title: "Completed task #1",
                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now,
                completed: .now
            ),
            .init(
                title: "Completed task #2",
                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now,
                completed: .now
            )
        ]
        
        for task in tasks {
            context.insert(task)
        }
    }

}